Re: [PATCH v2] perf evsel: Improve callchain warning for s390

[Jens Remus <jremus@linux.ibm.com>]

On 8/21/2026 2:55 PM, Jens Remus wrote:

> Instead, warn on s390 when callchain sampling is requested with an event
> provided by the CPUMSF hardware PMU, because that combination is not
> supported.

> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c

> @@ -1078,9 +1078,8 @@ static void __evsel__config_callchain(struct evsel *evsel, const struct record_o
>  	bool function = evsel__is_function_event(evsel);
>  	struct perf_event_attr *attr = &evsel->core.attr;
>  
> -	if (EM_HOST == EM_S390 && param->record_mode == CALLCHAIN_FP) {
> -		pr_warning_once(
> -			"Framepointer unwinding lacks kernel support. Use '--call-graph dwarf'\n");
> +	if (EM_HOST == EM_S390 && evsel->pmu && !perf_pmu__is_software(evsel->pmu)) {
> +		pr_warning_once("Cannot use hardware CPUMSF event with -g and --call-graph.\n");

Jan, Thomas, could you please do me a favor and test whether this works
as expected on LPAR with CPUMSF?  Time was running out before I leave on
vacation.

>  	}
>  
>  	evsel__set_sample_bit(evsel, CALLCHAIN);
Thanks and regards,
Jens
-- 
Jens Remus
Linux on Z Development (D3303)
jremus@de.ibm.com / jremus@linux.ibm.com

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